Elizabeta Baranovskaya was once a Russian-born ballerina, who had practiced since she was four years old. She was a student at the Moscow State Academy and her hometown was in Smolensk, but her mother was a Belarusian. Elizabeta's dream was to dance at the Bolshoi Theater (it was also once her mother's dream), but after learning of a tumor, she went to Italy to see about curing it, where her leg was unfortunately amputated. Because of this, she attempted suicide by jumping off the hospital roof and plummeting to the ground, but was unsuccessful; instead, she was retained at the hospital until the SWA stepped in.

Alessandro Ricci, her handler, renamed her Petrushka (for the Russian puppet Petrushka, and like Rico, it is a boy's name), and she underwent the physical augmentation process. Unlike the previous first-stage cyborgs, most of Petrushka's features were replaced, so she is not a natural redhead nor are her eyes naturally green (the doctor working to replace her body decided to model her after his first love, as Alessandro refused to specify any particular changes except that she "not be a redhead"). Furthermore, she is 16 years old therefore having a body of a teenager, unlike the rest of the girls who are children. Like Angelica was the first-stage prototype, Petrushka is the prototype for the second-stage generation and debuts in volume six, where she is also featured on the cover with her primary weapon. As a second-stage cyborg, Petrushka already had everything she needed to know about her life at the SWA pre-programmed into her brain; she knew where she was, that she would be trained for combat, and that she "must follow Alessandro's and the Agency's orders without hesitation," but an error occurred, and she has no memories, fake or otherwise. Any order that she is given she is forced to see out despite her own wishes, and she is forbidden to speak ill of her handler.

Her name is often shortened to the more feminine "Petra." Petrushka's preferred weapons are the Spectre M4 SMG and Taurus PT92 pistol.

Although she is left out of the anime adaption she has a small cameo in episode 5 of Gunslinger Girl -Il Teatrino-.